1. Field of the Invention
The present invention relates to a fuel injection control apparatus for an internal combustion engine. More particularly, the invention is concerned with a fuel injection control apparatus for the internal combustion engine in which fuel injectors are provided in association with individual engine cylinders, respectively, wherein the fuel injection control apparatus is designed for effectuating simultaneous injection of fuel for all the cylinders upon engine starting operation.
2. Description of Related Art
In the art, there has already been proposed for the internal combustion engine (hereinafter also referred to simply as the engine) in which the fuel injectors are provided on the cylinder-by-cylinder basis, such a fuel injection control apparatus which is designed for effectuating the step of simultaneous injection of fuel for all the cylinders of the engine upon starting operation thereof. In general, such fuel injection control apparatus is designed to carry out a cylinder identification process or routine and a simultaneous fuel injection process in the engine starting operation mode.
Of the two processes mentioned above, the cylinder identification process or routine is destined for identifying the cylinders for ignition on the basis of a crank angle signal outputted from a crank angle sensor while cranking the engine by means of an engine starter.
On the other hand, the engine starting simultaneous fuel injection process is carried out in succession to the above-mentioned cylinder identification process, whereby the fuel is simultaneously injected for all the cylinders while allowing the ignition to take place in the cylinders identified through the cylinder identification process to thereby crank the engine under the explosion energy. This simultaneous fuel injection process is carried out until the explosion within the cylinders has become stabilized, i.e., until the complete or perfect explosion takes place.
More specifically, in the engine starting simultaneous fuel injection process, the fuel is simultaneously injected for all the cylinders of the engine. In that case, the fuel quantity which corresponds to a quotient resulting from the division of the fuel quantity required or demanded for the combustion by the number N of the cylinders is injected under the timing of the crank angle signal as the basic fuel quantity to be injected at one time.
In this conjunction, it is noted that the conventional fuel injection control apparatus known heretofore is designed to inject the basic quantity of fuel after the cylinder identification process has been completed in the engine starting operation mode.
At this juncture, let""s represent the fuel quantity required for the single combustion by Fs, while representing by Fb the basic fuel injection quantity for one simultaneous fuel injection in the engine having N cylinders in the engine starting simultaneous fuel injection process. Then, the following expression applies valid.
Fb=Fs/Nxe2x80x83xe2x80x83(1) 
The conventional fuel injection control apparatus described above suffers a problem that a lot of time is taken for starting the engine operation because N steps are required for injecting the fuel quantity required for the combustion. In other words, the engine starting operation is accompanied with a noticeable time lag, to a disadvantage.
Furthermore, in the state where the cylinder identification has not been completed, the fuel injection is disabled. Consequently, even after the identification of cylinders allowing the ignition has been completed, not a little time is taken until the fuel injected actually contributes to the combustion, involving a delay in the initial explosion to another disadvantage.
In the light of the state of the art described above, it is an object of the present invention to provide a fuel injection control apparatus for the internal combustion engine which is capable of expediting the initial explosion and hence enhancing the engine starting performance.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a fuel injection control apparatus for an internal combustion engine, which apparatus includes a crank angle sensor for generating a crank angle signal indicative of angular position of a crank shaft of an internal combustion engine, various types of sensors for detecting operation states of the internal combustion engine, fuel injectors provided on a cylinder-by-cylinder basis for injecting demanded quantities of fuel for individual cylinders, respectively, a cylinder identifying means for identifying discriminatively the individual cylinders on the basis of the crank angle signal to thereby generate a cylinder identification signal, a fuel injection control means for controlling actuation of the fuel injectors of the individual cylinders, respectively, on the basis of the crank angle signal, an engine operation state signal derived from the outputs of the sensors and the cylinder identification signal, and a fuel injection quantity correcting means for correcting time durations for which the fuel injectors are driven upon every fuel injection on the basis of the crank angle signal, the engine operation state signal and the cylinder identification signal.
By virtue of the arrangement of the fuel injection control apparatus described above, the engine starting operation can be carried out with enhanced stability.
In a mode for carrying out the invention, the fuel injection control means should preferably be so designed as to effectuate the simultaneous fuel injection by driving the fuel injectors before the cylinder identification has been completed.
Owing to the arrangement mentioned above, the initial explosion can be expedited and hence the engine starting performance can significantly be improved.
In another mode for carrying out the invention, the fuel injection control means should preferably be so designed as to effectuate the simultaneous fuel injection by driving the fuel injectors one step before completion of the cylinder identification process.
With the arrangement mentioned above, the initial explosion can be expedited and hence the engine starting performance can significantly be improved.
In a further mode for carrying out the invention, the fuel injection control means should preferably be so designed as to effectuate the simultaneous fuel injection by driving the fuel injectors before the cylinder identification has been completed unless current operation is engine restarting operation while inhibiting the simultaneous fuel injection before the cylinder identification has been completed in the engine restarting mode. In this conjunction, the phrase xe2x80x9cengine restarting operationxe2x80x9d means the engine starting operation which is carried out in succession to a preceding engine starting operation which failed to bring about the complete explosion.
With the arrangement described above, such situation can positively be evaded that the quantity of fuel within the combustion system becomes excessive due to admixture of the fuel charged initially through the first simultaneous injection and the fuel injected for the engine restarting operation.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.